Blowers are used in the drying section of vehicle wash systems. In both conveyor/tunnel-type wash systems and “roll-over” type vehicle wash systems, the drying section is typically located just before the vehicle exits the wash system. The drying section of a wash system may be comprised of a plurality of air blowers mounted on a frame. The air blowers are employed to dry the vehicles by forcing a stream of air over the surface of the vehicle. The stream of air may also be heated above ambient temperature. Such blowers are commonly referred to as “dryers” in vehicle wash systems.
Each dryer typically has an outer housing or plenum enclosing a cavity that contains an impeller. The impeller may be connected to, and rotated by, the drive shaft of a motor. The motor may be an electric motor. The motor causes the impeller to draw in the gas (e.g. air) into the plenum, compress it, and then expel the compressed gas through an exit port, from the plenum. The exit port may have a nozzle associated therewith, to assist in directing the flow of air. The result is that a blower employed in a vehicle wash system can direct a high speed and volume of airflow over a vehicle surface to rapidly dry the vehicle before it exits the wash system.
The operation of blowers in vehicle wash systems may be controlled by a controller. For example, to conserve power, a relatively simple controller can be provided that is operable to switch the supply of power to the motor on and off, depending upon whether or not a vehicle is in the drying section of the vehicle wash system. The presence of a vehicle in the drying section can be detected by a known type of sensor. However, such blower control systems do not significantly address the intermittent nature of vehicle traffic in a wash system. It is not desirable to simply start and stop the blower motors as each vehicle passes into and out of the drying section.
It should be noted that starting and stopping an electric motor to achieve intermittent blower operation is disadvantageous. For example, when an electric motor is started, it generates a high transient peak load and often a large amount of heat. The high peak load may be undesirable as wash system operators may be charged more by their electrical utilities if there are peaks in their electricity demand, resulting in higher operational costs. The high peak load generated when starting an electric motor is compounded in a wash system since the drying section may have a plurality of blowers, many of which may be started at approximately the same time.
Also, frequently starting and stopping a blower motor decreases the life span of the motor, resulting in overall higher operating costs. Additionally, the large amount of heat generated upon starting and stopping an electric motor limits the rate at which the motor may be started and stopped. The amount of heat generated may be so significant that the blower cannot feasibly be started and stopped for each vehicle. Furthermore, starting and stopping the blower motor is relatively slow and may limit the capacity of the drying section.
However, operating the motors continuously under load results in unnecessary wear and tear on the blowers and is not energy efficient, both factors resulting in increased operating costs. A further disadvantage of continuously operating the blowers is that the blowers when being operated under load create a high noise level, particularly when no vehicle is present in the drying section to dampen the sound.
Previous attempts have been made to try to overcome some of these problems, but these methods are deficient in other ways. For example, a variable speed motor (variable frequency drive motor) could be employed, but there are significant additional costs associated with such motors. Additionally, variable speed motors may result in higher levels of electrical noise, compared to constant speed motors.
It is also known to operate the blower motor continuously, but having an outlet valve device, whereby the exit port is only opened when a vehicle is in position to be dried. This approach allows the fan to be operated under a reduced load when the exit port is closed, reducing electricity usage and noise. However, restricting or blocking the exit port creates an undesirable back-pressure that may reduce the life span of the blower components. Furthermore, to limit the flow through the exit port, the components must be capable of providing sufficient force to overcome the high velocity airflow to secure the closure of the exit. Consequently, placing the control mechanism at the exit port results in increased cost and places the control system and other blower components under increased stress.
It is also known to control the flow of air through a blower in a vehicle wash system by controlling the flow at the inlet using one or more damper devices. However, there are significant disadvantages to the known inlet control devices, particularly in the manner in which the flow of air into an air blower is regulated. Sustainable operation of known blower systems in wash systems at less than full capacity has proved difficult in the past. For example, it is known to employ a valve plate as a valve mechanism to control the amount of air entering the blower; however this results in an unbalanced load being distributed over the impeller when the intake damper is not in the fully open or fully closed positions. Similarly, it is known to employ louvers to block the air flow at the inlet, but this may disturb the uniformity of the air entering the blower when rotated to a partially open position and provide non-uniform input air flow on the impeller. The louvers may also be required to be positioned a minimum distance from the impeller for optimal performance, particularly if rotated to a partially open position, rendering it difficult to design a compact blower system.
Additionally, known systems for drying vehicles do not accommodate variations in the types of vehicle being dried or distinguish between different part of the same vehicle, by varying the amount of air flow directed to the vehicle or specific parts thereof.
Accordingly, a vehicle drying system with an improved air flow control system for the air blowers, is desired.